Re: [2.4.26] overcommit_memory documentation clarification

From: Vincent Lefevre
Date: Sun May 09 2004 - 16:52:37 EST

On 2004-05-09 14:06:11 -0700, Paul Jackson wrote:
> Vincent wrote:
> > NULL == (void *) 0 and NULL == 0 must be true
> Yes - NULL is compares equal to both (void *)0 and 0.
> No - not necessarily the _same_ value - one could be
> on a system with 32 bit ints, 64 bit pointers, for example.

And so?

> > The goal of malloc is to reserve memory.
> It's up to the kernel whether sbrk (used by malloc to
> obtain virtual address space) reserves memory or not.

More old_mmap than brk (BTW, I forgot to say that this was on
an x86 machine, I don't know if this matters...).

> Check out:
> /proc/sys/vm/overcommit_memory
> Documentation/sysctl/vm.txt - overcommit_memory

But the documentation is wrong (on an official 2.4.26 kernel).
It seems that there is no way to get malloc() always return 0
when there isn't enough memory, even in simple cases (see my
program posted in the first message).

Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <>
100% validated (X)HTML - Acorn / RISC OS / ARM, free software, YP17,
Championnat International des Jeux Mathématiques et Logiques, etc.
Work: CR INRIA - computer arithmetic / SPACES project at LORIA
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